Allow user to set the "hasPrefix" function in Complete()

complete.go

@@ -45,13 +45,35 @@ func (c *Complete) Run() bool {
 	return c.Complete()
 }
 
+type completeArgs struct {
+	prefixMatcher func(str, prefix string) bool
+}
+
+//CompleteArg is a config argument for Complete.Complete
+type CompleteArg func(*completeArgs)
+
+//WithMatcher causes Complete to use the given matcher function when filtering completion options
+func WithMatcher(matcher func(str, prefix string) bool) CompleteArg {
+	return func(configs *completeArgs) {
+		configs.prefixMatcher = matcher
+	}
+}
+
 // Complete a command from completion line in environment variable,
 // and print out the complete options.
 // returns success if the completion ran or if the cli matched
 // any of the given flags, false otherwise
 // For installation: it assumes that flags were added and parsed before
 // it was called.
-func (c *Complete) Complete() bool {
+func (c *Complete) Complete(configSetters ...CompleteArg) bool {
+	cfg := &completeArgs{
+		prefixMatcher: strings.HasPrefix,
+	}
+
+	for _, configSetter := range configSetters {
+		configSetter(cfg)
+	}
+
 	line, point, ok := getEnv()
 	if !ok {
 		// make sure flags parsed,
@@ -72,7 +94,7 @@ func (c *Complete) Complete() bool {
 	// filter only options that match the last argument
 	matches := []string{}
 	for _, option := range options {
-		if strings.HasPrefix(option, a.Last) {
+		if cfg.prefixMatcher(option, a.Last) {
 			matches = append(matches, option)
 		}
 	}

complete_test.go

@@ -13,6 +13,14 @@ import (
 func TestCompleter_Complete(t *testing.T) {
 	initTests()
 
+	buildCompleteArgs := func(args ...CompleteArg) []CompleteArg {
+		return args
+	}
+
+	permissiveMatcher := func(str, prefix string) bool {
+		return true
+	}
+
 	c := Command{
 		Sub: Commands{
 			"sub1": {
@@ -40,14 +48,16 @@ func TestCompleter_Complete(t *testing.T) {
 	cmp := New("cmd", c)
 
 	tests := []struct {
-		line  string
-		point int // -1 indicates len(line)
-		want  []string
+		line         string
+		point        int // -1 indicates len(line)
+		want         []string
+		completeArgs []CompleteArg
 	}{
 		{
-			line:  "cmd ",
-			point: -1,
-			want:  []string{"sub1", "sub2"},
+			line:         "cmd ",
+			point:        -1,
+			want:         []string{"sub1", "sub2"},
+			completeArgs: buildCompleteArgs(WithMatcher(permissiveMatcher)),
 		},
 		{
 			line:  "cmd -",
@@ -69,6 +79,17 @@ func TestCompleter_Complete(t *testing.T) {
 			point: -1,
 			want:  []string{"sub1", "sub2"},
 		},
+		{
+			line:  "cmd SuB",
+			point: -1,
+			want:  []string{},
+		},
+		{
+			line:         "cmd SuB",
+			point:        -1,
+			want:         []string{"sub1", "sub2"},
+			completeArgs: buildCompleteArgs(WithMatcher(permissiveMatcher)),
+		},
 		{
 			line:  "cmd sub1",
 			point: -1,
@@ -262,7 +283,7 @@ func TestCompleter_Complete(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(fmt.Sprintf("%s@%d", tt.line, tt.point), func(t *testing.T) {
-			got := runComplete(cmp, tt.line, tt.point)
+			got := runComplete(cmp, tt.line, tt.point, tt.completeArgs)
 
 			sort.Strings(tt.want)
 			sort.Strings(got)
@@ -349,7 +370,7 @@ func TestCompleter_Complete_SharedPrefix(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.line, func(t *testing.T) {
-			got := runComplete(cmp, tt.line, tt.point)
+			got := runComplete(cmp, tt.line, tt.point, nil)
 
 			sort.Strings(tt.want)
 			sort.Strings(got)
@@ -364,15 +385,15 @@ func TestCompleter_Complete_SharedPrefix(t *testing.T) {
 // runComplete runs the complete login for test purposes
 // it gets the complete struct and command line arguments and returns
 // the complete options
-func runComplete(c *Complete, line string, point int) (completions []string) {
+func runComplete(c *Complete, line string, point int, completeArgs []CompleteArg) (completions []string) {
 	if point == -1 {
 		point = len(line)
 	}
 	os.Setenv(envLine, line)
 	os.Setenv(envPoint, strconv.Itoa(point))
 	b := bytes.NewBuffer(nil)
 	c.Out = b
-	c.Complete()
+	c.Complete(completeArgs...)
 	completions = parseOutput(b.String())
 	return
 }